A general need exists for devices to prevent return flow of fluid, for instance under conditions of under pressure, in order to prevent the penetration of air into a fluid supply line, or the return to the supply duct of a fluid which has already passed therethrough. In water supply applications, there is significant interest in preventing a return flow of water into the supply line, since the water quality may degrade due to the return flow. In order to prevent return flow, it is known to use check valves whose moveable valve closing members are subjected to spring action in the direction of a valve seat which is provided in the housing of the check valve. Examples of check valves are provided in U.S. Pat. Nos. 3,378,030; 3,612,097; 4,605,041; 5,482,080; and 5,664,602, as well as the patents referenced therein.
Despite the existence of a large number of check valve designs, there is a continuing need for enhanced, simple, reliable check valve designs. The present invention is thus directed to providing an enhancement to the existing state of check valve designs.